Being both inexpensive and reasonably stable, stucco is often employed in the construction industry for either a residential or a commercial building. Such stucco is especially popular in warm climates.
Stucco is often used with wood or metal framing. The resulting framed structure breathes, i.e. expands and contracts in response to daily thermal stresses. This breathing may result in the development of small cracks and other imperfections in the stucco.
Extreme weather conditions (e.g., a high summer heat coupled with a very low humidity, as found in the desert regions of the southwestern U.S.) may result in incomplete or irregular curing of stucco. Incomplete or irregular curing may in turn result in weak, cracked, and efflorescent stucco. For example, excessive heat and insufficient humidity may lead to the early release of water from newly applied stucco, resulting in incompletely hydrolized cement. The intrusion of water onto and into this incompletely hydrolized cement (e.g., from rain or sprinklers) can result in severe cracking and efflorescence.
It is a problem that standard architectural coatings generally cannot keep water from entering into stucco. Such coatings are therefore ineffective in protecting stucco against water intrusion and the resulting damage.
Elastomeric coatings have been used for some time to inhibit failures in stucco, and have been successful to a limited degree. A high-quality all-acrylic elastomeric coating will, when properly applied with an adequate film build, accomplish the task of protecting stucco from water intrusion. Unfortunately, the use of elastomeric coatings has several drawbacks.
The cost of materials for elastomeric coatings is three to four times the cost of a high-quality acrylic flat. Similarly, the cost of labor to apply elastomeric coatings is four to five times the cost of a standard paint job. This results in a tendency to perform an inadequate job of application by skimping on paint quality and/or coverage. This in turn results in failures ranging from cracking and efflorescing of the stucco to blistering of the elastomeric coating due to trapped moisture.
Additional problems exist in the repair of cracked stucco. Traditionally, such cracks are filled using an elastomeric caulk. The surface is then repainted. In many cases, the caulked crack is visible through the paint film. This results in a minimal improvement in appearance over the unrepaired cracks, and/or necessitates the application of a second coat of paint. The repair of stucco is therefore labor intensive and not always comprehensive.